diff --git a/3rdparty/fmtlib-src b/3rdparty/fmtlib-src
new file mode 160000
index 0000000..a337011
--- /dev/null
+++ b/3rdparty/fmtlib-src
@@ -0,0 +1 @@
+Subproject commit a33701196adfad74917046096bf5a2aa0ab0bb50
diff --git a/3rdparty/googlebenchmark-src b/3rdparty/googlebenchmark-src
new file mode 160000
index 0000000..361e8d1
--- /dev/null
+++ b/3rdparty/googlebenchmark-src
@@ -0,0 +1 @@
+Subproject commit 361e8d1cfe0c6c36d30b39f1b61302ece5507320
diff --git a/3rdparty/googletest-src b/3rdparty/googletest-src
new file mode 160000
index 0000000..1546095
--- /dev/null
+++ b/3rdparty/googletest-src
@@ -0,0 +1 @@
+Subproject commit 15460959cbbfa20e66ef0b5ab497367e47fc0a04
diff --git a/include/libimp/result.h b/include/libimp/result.h
index 5ab78a7..f733556 100644
--- a/include/libimp/result.h
+++ b/include/libimp/result.h
@@ -132,8 +132,6 @@ class result : public TypeTraits {
 public:
   using type_traits_t = TypeTraits;
 
-  result() noexcept = default;
-
   template <typename... A, 
             typename = is_not_match<result, A...>,
             typename = decltype(type_traits_t::init_code(std::declval<result_code &>()
diff --git a/src/libimp/fmt.cpp b/src/libimp/fmt.cpp
index 39c34f2..3eae1ed 100644
--- a/src/libimp/fmt.cpp
+++ b/src/libimp/fmt.cpp
@@ -7,6 +7,7 @@
 #include <cstring>    // std::memcpy
 #include <algorithm>  // std::min
 #include <initializer_list>
+#include <cstdint>
 
 #include "libimp/codecvt.h"
 
@@ -116,16 +117,16 @@ span<char> fmt_of_float(span<char const> fstr, span<char const> const &l) {
 
 template <typename A /*a fundamental or pointer type*/>
 int sprintf(fmt_context &ctx, span<char const> const &sfmt, A a) {
-  for (int sz = -1;;) {
+  for (std::int32_t sz = -1;;) {
     auto sbuf = ctx.buffer(sz + 1);
-    if (sbuf.size() < (sz + 1)) {
+    if (sbuf.size() < std::size_t(sz + 1)) {
       return -1;
     }
     sz = std::snprintf(sbuf.data(), sbuf.size(), sfmt.data(), a);
     if (sz <= 0) {
       return sz;
     }
-    if (sz < sbuf.size()) {
+    if (std::size_t(sz) < sbuf.size()) {
       ctx.expend(sz);
       return sz;
     }
diff --git a/test/imp/test_imp_span.cpp b/test/imp/test_imp_span.cpp
index 630bca2..0304f7e 100644
--- a/test/imp/test_imp_span.cpp
+++ b/test/imp/test_imp_span.cpp
@@ -20,7 +20,7 @@ TEST(span, span) {
   auto test_proc = [](auto &&buf, auto &&sp) {
     EXPECT_EQ(imp::countof(buf), sp.size());
     EXPECT_EQ(sizeof(buf[0]) * imp::countof(buf), sp.size_bytes());
-    for (int i = 0; i < sp.size(); ++i) {
+    for (std::size_t i = 0; i < sp.size(); ++i) {
       EXPECT_EQ(buf[i], sp[i]);
     }
   };